Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.47	13.690%	$114.2243	$114.22	$114.20	$114.20
Purchase #2	$247.40	13.762%	$281.4472	$281.45	$281.45	$281.40
Purchase #3	$83.82	8.363%	$90.8299	$90.83	$90.85	$90.80
Purchase #4	$191.56	10.676%	$212.0109	$212.01	$212.00	$212.00
Purchase #5	$230.35	11.261%	$256.2897	$256.29	$256.30	$256.30
Purchase #6	$40.33	10.469%	$44.5521	$44.55	$44.55	$44.60
Purchase #7	$237.27	7.299%	$254.5883	$254.59	$254.60	$254.60
7 purchase totals =	$1,131.20		$1,253.9424	$1,253.94	$1,253.95	$1,253.90